MEMPHIS, TENN. — The neon lights of Memphis fade as you cross the city line into Bartlett, Tennessee, where the memories of a woman’s mysterious disappearance never fade.

Andrea Fox, friend: Any time I see a missing person’s report, I relive that night. Just wondering where could she be. What happened that night?

Andrea is talking about her friend Cherryl Pearson, a 37-year-old doctor, who left behind more clues than in many missing person cases. Four agonizing years later, her parents are still waiting for an answer, still struggling every single day.

Hazel Pearson, mother: When you do something to one person, it’s a ripple effect. It affects a lot of people for a long, long time.

Cherryl is the youngest of Hazel and Leon Pearson’s three children. A high achiever who earned a degree in chemical engineering, Cherryl then completed med school, and became a well-respected pediatrician.

Rob Stafford, Dateline correspondent: You must be incredibly proud of her.

Leon Person, father: Yeah. No doubt about it. Yes sir.

Cherryl accomplished all that even though she was a severe diabetic. She was independent but over the years remained very close to her parents. They last heard from her when she called from a Memphis Grizzlies basketball game on Friday night, January 4th, 2002. Cherryl, who was single and a season ticket holder, went to the game alone.

Cherryl drove home from the game around 10:30 that night. Andrea Fox and another friend stopped by to visit.

Fox: She seemed fine.

Stafford: Was she expecting to see anyone that night?

Fox: No, not that night. She did mention that her sister was going to work early the next morning and was going to drop off the kids. She loved those children and she spent a lot of time with them. She was excited to see them the next morning.

Andrea and her friend left about 1 a.m. Cheryl’s sister arrived early the next morning to drop off her kids but Cheryl, who was supposed to babysit, was gone... and so was her car.

Stafford: How do you know she didn’t just leave on her own accord?

Hazel: I don’t know.

Frantic, they called police, at first fearing their daughter had become disoriented by her diabetes and might have driven off the road. Colleagues from her medical practice hit the streets to search and hand out fliers but there was no sign of Cherryl.

When police checked Cherryl’s phone records, right away something stood out: About an hour after her friends left, someone called her house at 1:58 a.m. in the middle of the night. It came from this pay phone at a convenience store about a half mile away. The call lasted just 5 seconds.

Stafford: And was the call answered?

Police inspector Steven Johnson: Yes, sir.

That tells Bartlett police inspector Steven Johnson and Detective Ken Lee that Cherryl was home when the call came in.

Johnson: It could be, “I’m on my way over.” “I’m down here at the service station. Meet me.”

Det. Ken Lee: It could’ve also just as easily been to see if she was home. She could’ve answered the phone, “Hello? Hello?” No response and they hung up.

They say that phone call was not the only odd thing about this case.

Stafford: You get to the house and what do you find?

Det. Lee: Find that the cell phone is on the table along with her pager. And incidentally, she was on call that evening. And so she would have those with her.

They’re important clues indicating to police she left suddenly. But was it by choice or by force? Police found no signs of a struggle at the house. And a few days later they found clues that were even more puzzling - inside Cherryl’s car, which was discovered at a nearby apartment complex.

Stafford: Any signs of a struggle inside the car?

Johnson: No, sir.

Stafford: Are the keys inside?

Johnson: Yes, sir. We found the keys. And in the trunk of her car is her medical bag. She apparently was carrying it like a purse ‘cause she had a lot of personal items in there, including the keys.

Car keys locked in her trunk. That told police she was the victim of foul play. But why?

Stafford: Any money left?

Lee: There was a $140 in 20s in a First Tennessee envelope.

Stafford: So as far as you could tell nothing was stolen.

Det. Lee: Correct. It tells me that the motive was not robbery.

And there was one more thing...

Det. Lee: The car was just too clean. It was cleaner than normal, detailed even.

Stafford: As though somebody had wiped away prints?

Det. Lee: Yes, sir—it’d been totally detailed. We didn’t even find her prints in there.

A quick call in the middle of the night, her cell phone and pager left behind, and no signs of a struggle: Those clues, at least, suggested to investigators Cherryl probably knew her assailant.

Stafford: Is there anyone within her circle of friends or relatives who has a criminal history?

Johnson: Yes, sir. She has a brother-in-law that has a criminal history of bank robbery.

Stafford: Does he have an alibi for January 4, 2002?

Johnson: He’s been interviewed and we’ve taken statements from him.

Stafford: Are you satisfied with the alibi for that night?

Det. Lee: No. There are certain inconsistencies that are not explainable.

Police also say Cherryl had a life insurance policy worth $150,000 - so far not paid out since there is no proof Cherryl is dead.

Stafford: Who is the beneficiary?

Johnson: Cherryl’s sister.

Stafford: Who’s married to the brother-in-law who served time for robbery.

Johnson: Yes, sir.

The brother-in-law, Chuck Hildreth, is the father of the children Cherryl was going to watch the day she disappeared. While police have expressed suspicions about him, they are not calling him a suspect. They say he’s denied any involvement in Cherryl’s disappearance and her parents told us they don’t believe he was responsible. Focusing on him, they say, is unfair.

The Pearsons say that no matter where the clues lead, no matter who’s responsible, they want to solve the mystery of what happened to their daughter.

Stafford: Do you think there’s any way Cherryl is alive?

Leon Pearson: At this point, I don’t think so.

Hazel Pearson: We still love her. You know she’s still a part of us and will be forever and ever.

Dateline wires the home of a volunteer, Jenny, from top to bottom with hidden cameras. Then she called repairmen to her house for a simple problem we created as a test with Jenny's pool. NBC's Chris Hansen reports.